Effects of injection duration on site-pain intensity and bruising associated with subcutaneous heparin

The research evaluated two subcutaneous heparin injection techniques to determine the effects of different injection duration (10- and 30-seconds) on site-pain intensity and bruising.

The research was instigated because nurses and patients in the hospital under investigation reported a high incidence of site-pain and bruising associated with subcutaneous heparin therapy. This research was conducted over a period of 7 months between September 1998 and April 1999. The Ethic Committees of the University and the hospital approved the research.

The research used a within-subjects, quasiexperiment, which would yield more convincing causal inferences, owing to the assumption that pain perception and physiological factors affecting coagulation varied less in the same subject than in two comparable subjects. The research involved 34 stroke patients receiving low-molecular weight heparin. For each subject, one of the two injection techniques was used as the first injection and 12 hours later the other injection technique as the second injection. Subjects rated the level of perceived site-pain intensity using the vertical visual analogue scale (VAS). Injection-site bruising were measured at 48 and 60 hours after each injection. Digital planimetry was used to measure the surface-area of bruise tracings. The final data set for analysis consisted of 68 VAS pain scores and 136 bruise sizes. As normality of the data could not met after transformations, Wilcoxon Signed-Rank tests were used to determine the effects caused by injection duration on site-pain and bruise size. The level of significance was determined at P < 0.05.

Results indicated that the 30-second duration injection technique resulted in significantly less intense site-pain and fewer and smaller bruises.

It was concluded that administering a subcutaneous heparin injection over longer duration reduces injection site-pain and bruising. However, the convenience, relatively small sample may limit the generalisability of the research findings.